Pneumatic system having noise reduction features for a medical fluid machine

ABSTRACT

A pneumatic system for a medical fluid machine operating a medical fluid cassette, the pneumatic system including an interface for supplying positive pneumatic pressure and negative pneumatic pressure to the medical fluid cassette; a source of positive pneumatic pressure; a source of negative pneumatic pressure; and a pneumatic pump including a first head and a second head, wherein the first head is dedicated to supplying positive pneumatic pressure to the positive pneumatic pressure source and the second head is dedicated to supplying negative pneumatic pressure to the negative pneumatic pressure source.

PRIORITY

This application claims priority to and the benefit as a continuationapplication of U.S. patent application Ser. No. 15/465,882, filed Mar.22, 2017, entitled, Pressure Manifold System For Dialysis, which iscontinuation application of U.S. patent application Ser. No. 14/627,072,filed Feb. 20, 2015, now U.S. Pat. No. 9,623,168, entitled, “PressureManifold System for Dialysis”, which is a continuation application ofU.S. patent application Ser. No. 13/919,297, filed Jun. 17, 2013, nowU.S. Pat. No. 8,961,444, entitled, “Pressure Manifold System forDialysis”, which is a continuation application of U.S. patentapplication Ser. No. 13/047,203, filed Mar. 14, 2011, now U.S. Pat. No.8,465,446, entitled, “Noise-Reducing Dialysis Systems And Methods OfReducing Noise In Dialysis Systems”, which is a divisional applicationof U.S. patent application Ser. No. 11/929,330, filed Oct. 30, 2007, nowU.S. Pat. No. 7,905,853, entitled, “Dialysis System Having IntegratedPneumatic Manifold”, the entire contents of each of which areincorporated herein by reference and relied upon.

BACKGROUND

The present disclosure relates generally to a medical fluid deliverysystem and in particular to a dialysis system. U.S. Pat. No. 5,350,357,the entire contents of which are incorporated herein by reference, showsa peritoneal dialysis machine 10 having housing 12. Housing 12 holds abag heater module 14 located under a bag heating plate 16. Housing 12further encloses a pneumatic actuator module 20. Pneumatic actuatormodule 20 incorporates a cassette holder 22 that holds a disposabledialysis cassette (not illustrated) and a liquid shutoff assembly 24.Machine housing 12 further encloses a source 30 of pneumatic pressureand an associated pneumatic pressure distribution module 40, which linksthe pressure source 30 with the actuator module 20. Pressuredistribution module 40 stores positive pressure in reservoir 32 andnegative pressure in reservoir 34. Machine housing 12 also encloses anAC power supply module 36 and a back-up DC battery power supply module38 to power machine 10.

Tubing 42 connects pneumatic valves located on pressure distributionmodule 40 to the machine components that operate using pneumaticpressure. Slots 44 in the side of the pressure distribution module 40accommodate the passage of the tubing 42. In particular, tubing 42 runsfrom pressure distribution module 40 to actuator module 20, where thetubing connects to components such as a cassette sealing bladder (notillustrated), an occluder bladder for liquid shutoff assembly 24 and topump and valve actuators that control the application of positive andnegative pressure to different areas of the disposable cassette.

Each of the tubes 42 has to be disconnected individually to removeeither pressure distribution module 40 to actuator module 20 frommachine 10. Tubes 42 are not easy to disconnect. Tubing 42 oftenstretches and becomes unusable when pulled off the barbed fittingsconnected to pressure distribution module 40. The barbed fittingsthemselves can be damaged if an attempt is made to cut tubes 42 off thefittings.

FIG. 2 shows pressure distribution module 40 exploded. Pressuredistribution module 40 includes a printed circuit board 46 which iscarried on stand-off pins 48 atop the pressure distribution module.Pressure transducers 50 mounted on printed circuit board 46 of module 40sense through associated sensing tubes 52 pneumatic pressure conditionspresent at various points along the air conduction channels (notillustrated) within pressure distribution module 40. Pressuretransducers 50 and/or the solder joint that connect the pressuretransducers to the printed circuit board 46 can be damaged if an attemptis made to disconnect the tubes between the manifold and the pressuretransducers.

Attempts to detach the tubing from actuator module 20 also encounterproblems. FIG. 3 shows a cassette interface 26, which is located insideactuator module 20. T-fittings 28 connect the tubing 42 to the ports ofthe valve actuators and pump actuators. Thus to remove actuator module20 from pressure distribution module 40, cassette interface 26 has to beaccessed first and then T-fittings 28 have to be removed from cassetteinterface 26.

A need therefore exists for a dialysis machine that is more readilyrepaired and maintained.

SUMMARY

The present disclosure relates to an integrated pneumatic manifold withdirect mounted or encapsulated parts that eliminate the need for certaintubes or hoses. The manifold can be used in medical fluid deliverytreatments, such as any type of dialysis treatment or machine, e.g., oneoperating on pneumatic pressure. The manifold can incorporate otherpneumatic components besides valves, such as one or more storagereservoir, a pressure pump and a manual diverter valve for calibrationstandard connection.

The manifold in one embodiment includes a printed circuit board (“PCB”)with pneumatic valve drives. The manifold also has easily removable portheaders with multiple tubing connections for tubes leading to othersubsystems. Valves attached to the PCB communicate with the ports of theheader via pneumatic traces or grooves formed in the plate to which thePCB and headers are mounted. The PCB containing the valve drivers alsoincludes a spike and hold circuit in one embodiment that minimizes theholding current required when the valves remain energized for more thana certain period of time, e.g., about 0.1 seconds.

The air pump is mounted in one embodiment to a lower manifold plate,which serves as a heat sink for the air pump motor. The lower plate cantherefore be made of a light, thermally conductive material, such asaluminum. The lower plate attaches to the upper plate holding the PCB,valves and headers via a gasket between the plates. The gasket seals thepneumatic pathways or grooves formed on the underside of the upperplate.

The port headers allow the manifold assembly to be detached easily fromthe dialysis machine, e.g., from a door assembly and electronics in themachine to which the ports and PCB are connected respectively. Any ofthe manifold subassembly, door subassembly or control board subassemblycan be removed and replaced without having to (i) replace any of theinterconnecting tubing or (ii) remove any other machine subassembly. Thepotential to damage any of the interconnecting components is accordinglyminimized. For example, tubing does not have to be detached from barbedports fittings, which otherwise can potentially damage the fitting inaddition to destroying the tubing.

A filter that prevents particles from entering the manifold is alsointegrated into the manifold. In a one embodiment, the filter is a flatfilter element that is sandwiched between the upper and lower plates ofthe manifold. As mentioned, pneumatic reservoirs (shown above asstand-alone positive and negative pressure source tanks 32 and 34) arealso integrated into the manifold in one embodiment. Many of the headerports to the valves connect directly into the reservoirs. Pressuretransducers can also connect directly into the reservoirs and arethereby unaffected by the transient dynamic conditions that occur in thepneumatic tubing when the system is operating. The manual diverter valveconnected to the assembly allows an external pressure standard to beconnected to the manifold during calibration to calibrate the pressuretransducers.

The manifold assembly works in a pneumatic system to operate a medicalfluid system such as a dialysis system. The manifold, for example, candeliver positive or negative air to dialysis fluid pump and valveactuators. The actuators actuate pump and valve chambers located on adisposable fluid cassette. The cassette needs to be sealed to a cassetteinterface (e.g., shown above as interface 26). In one embodimenttherefore the manifold assembly also provides pressure to a bladder thatpresses the cassette against the cassette interface for operation. Tubesconnected to the cassette receive dialysis fluid, carry fresh dialysisfluid to the patient, and carry spent dialysis fluid from the patient todrain. When the machine is not in use or in the event that the machineloses power, the tubes are crimped closed via a spring-loaded occluderthat crimps the tubing unless otherwise acted upon. In one embodiment,the manifold assembly pressurizes a second bladder, which operates toretract the occluder to uncrimp or open the tubing.

In the pneumatic system of the present disclosure, the air pumppressurizes four separate tanks, namely, the positive and negativereservoirs located on the manifold assembly, the cassette sealingbladder and the occluder bladder. The pneumatic configurations shownbelow include apparatuses that allow the air pump to pressurize each ofthe tanks and bladders individually so that one does not “steal”pressure or air from another during operation of the machine. Forexample, the air pump located on the manifold assembly in one embodimentincludes dual pump heads, which can be dedicated to pumping positive andnegative pressure, respectively, to the positive and negativereservoirs. Indeed, the pump can pump to the positive and negativereservoirs simultaneously. This has been found to have the added benefitof halving the pump output to each reservoir, reducing noise.

The pneumatic system isolates the reservoirs from the bladders and thebladders from each other using valves. To conserve the number of valves,the system in one embodiment uses a three-way valve to supplypressurized air to either a positive pressure tank for operating thefluid pumps or to a line that supplies a cassette sealing bladder and atubing pumping occluder bladder. Also, to conserve the number ofsolenoid valves needed, the system in one embodiment places a checkvalve in a split in a line that supplies pressure to the cassettesealing bladder and occluder bladders, such that the occluder bladdercannot steal positive pressure from the cassette sealing bladder. A dropin the cassette sealing bladder pressure can compromise the seal of thedialysis pumping cassette relative to the dialysis instrument.

It is accordingly an advantage of the present disclosure to provide apneumatic manifold assembly having improved reliability, ease ofassembly and serviceability while being backwards compatible withexisting systems.

It is another advantage of the present disclosure to provide a pneumaticmanifold assembly that integrates the air pump, heat sinks the air pumpand places the air pump inside a sealed enclosure to minimize the noisewithout overheating the pump and valves.

It is a further advantage of the present disclosure to mitigate dialysisinstrument noise.

It is still another advantage of the present disclosure to provide avalve manifold assembly configured to isolate two separate sealingbladders pressurized via the manifold assembly.

It is yet a further advantage of the present disclosure to provide arobust pneumatic system in which pneumatic storage tanks and bladdersare pneumatically isolated form one another.

Additional features and advantages are described herein, and will beapparent from, the following Detailed Description and the figures.

BRIEF DESCRIPTION OF THE FIGURES

FIGS. 1 to 3 are various perspective views of a prior art peritonealdialysis machine and in particular to a pneumatic system of the machine.

FIG. 4 is a perspective view of one embodiment of a pressure manifoldassembly of the present disclosure.

FIG. 5 is another perspective view of the pressure manifold assembly ofFIG. 4.

FIG. 6 illustrates one embodiment of a pressure manifold plate havingpneumatic passageways, the plate operable with the pressure manifoldassembly of the present disclosure.

FIG. 7 is a perspective view of the underside of top plate 102 from thepressure manifold assembly of FIG. 4.

FIG. 8 is an exploded perspective view of a lower portion of thepressure manifold assembly of FIG. 4.

FIGS. 9A to 9D are perspective views of an alternative pressure manifoldassembly of the present disclosure.

FIGS. 10 and 11 are schematic views of various pneumatic configurationsfor the pressure manifold assembly and other pneumatic components of thepresent disclosure.

FIGS. 12 and 13 illustrate one embodiment of a noise reduction circuitoperable with the pneumatic pump of the pressure manifold assemblies ofthe present disclosure.

DETAILED DESCRIPTION Pneumatic Hardware Configurations

Referring now to the drawings and in particular to FIGS. 4 to 8,pressure manifold assembly 100 illustrates one embodiment of the presentdisclosure. Assembly 100 includes a top plate 102, a bottom valve plate104 and a gasket 106 sandwiched between top plate 102 and bottom valveplate 104. Top plate 102 can be made of aluminum or other lightweightmaterial that can be threaded or fitted with threaded inserts.

Manifold assembly 100 includes a first header 108, which is attached tomanifold top plate 102 in a sealed manner using o-ring seals 110 andscrews 112. O-Ring seals 110 provide a leak tight connection between allof the internal passageways 134 (see FIG. 7) connecting first header 108to manifold top plate 102. A plurality of hose barbs 114 on first header108 connect the pneumatic passages of first header 108 to the pilotoperated valves and pumps contained in actuator assembly (shown above inFIG. 1) using flexible urethane tubing (not shown) for example. Theactuator assembly (shown above in FIG. 1) can be separated readily frommanifold assembly 100 by removing screws 112.

Manifold assembly 100 includes a second header 116, which is also isattached to manifold top plate 102 in a sealed manner using o-ring seals110 and screws 112. O-Ring seals 110 provide a leak tight connectionbetween all of the internal passageways connecting second header 116 tomanifold top plate 102. A plurality of hose barbs on second header 116connect the pneumatic passages of second header 116 to pressuretransducers contained in a separate printed circuit board assembly,which is similar to item 40 shown in FIG. 2 of the prior art usingflexible urethane tubing (not shown). The pressure transducer printedcircuit board 40 can be separated readily from manifold assembly 100 byremoving screws 112 and is attached to header 116 via flexible, e.g.,urethane, tubing only.

Referring now to FIG. 7, the underside of plate 102 (from that shown inFIGS. 4 and 6) is illustrated. Internal passageways 134, discussedabove, pneumatically connect hose barbs 114 on first header 108 to portsof the right bank of valves 120 shown in FIG. 6. Likewise, internalpassageways 138 pneumatically connect hose barbs 114 on second header116 to the left bank of valves 120 in FIG. 6. Some of the otherpassageways in FIG. 7 are used to connect air pump heads 156 to filter136, air tanks 140 and manual valve 130 as shown in schematics 200 and210. There are also passageways in FIG. 7 that connect the right andleft pump chambers (L_DISP and R_DISP), the right and left volumetricreference volumes (VSL and VSR), and their respective pressure sensorsto the solenoid valves with which they communicate when pumping fluidand when measuring the volume of fluid that has been pumped.

Conversely, manifold assembly 100 can be removed from the machine bydisconnecting headers 108 and 116 and removing an electrical connectionto printed circuit board (“PCB”) 118 from the PCB. PCB 118 controlsvalves 120.

PCB assembly 118 is placed in a recessed channel 122 in top plate 102via shorter screws 124 before valves 120 are attached to top plate 102via small screws 126. Electrical contact pins (not seen) extend downfrom valves 120 and plug into mating connectors (not seen) soldered toPCB assembly 118. Any of valves 120 can be removed easily and replacedby removing the two small screws 126.

Printed circuit board 118 contains a spike and hold circuit thatenergizes each of valves 120 with a twelve volt voltage spike and thenreduces the applied voltage to a hold level to save energy and reducethe heat that valve 120 produces when it is held open. For example, thespike and hold circuit can reduce the supply voltage from twelve voltsto 8.48 volts, which reduces the energy that needs to be dissipated(heat generated) up to fifty percent of that generated at twelve volts.

In an alternative embodiment, the spike and hold circuit is stored insoftware, e.g., via a memory and processor soldered to PCB 118. Here,smart power proportioning varies the spike duration depending upon howlong it has been since the particular valve 120 has been actuated. Forexample, the processing and memory can set a spike duration for a valve120 that has not been actuated recently to two-hundred milliseconds, andalternatively set a spike duration for a valve 120 that is continuouslyoperated to only fifty milliseconds, further saving energy and reducingheat generation. The ability to vary the voltage profile that is appliedto actuate solenoid valve 120 not only minimizes the heat that the valvegenerates (reducing the operating temperature of the valve), thevariation also minimizes the amount of audible noise that valve 120generates when energized. Reduced audible noise is especiallyadvantageous when the dialysis machine is used at the patient's bedside,such as with a home peritoneal dialysis or home hemodialysis machine.

A diverter valve 130 is attached directly to top plate 102 via screws112. Diverter valve 130 includes two ports on its underside, which sealto manifold 100 using o-rings 110 as shown in FIG. 6. Rotation of theslotted screw opposite an external port 132 of valve 130 connects theunderside ports of valve 130 fluidly to port 132. External Port 132 inturn connects fluidly to an external pressure standard (not illustrated)for calibration of the pressure transducers. Rotating slotted screw toits original position blocks port 132, while enabling the two ports onthe underside of diverter valve 130 to communicate fluidly.

A particulate filter 136 is sandwiched between top valve plate 102 andbottom valve plate 104. Gasket 106 seals top valve plate 102 to bottomvalve plate 104 and to particulate filter 136.

FIGS. 5 and 8 show molded, cast or machined pneumatic reservoirs 140mounted to bottom plate 104 using screws 112. Pneumatic reservoirs 140hold pressurized air for valves 120 to supply the pressurized air todifferent subsystems within the dialysis instrument. For example, valves120 supply pressurized air to the fluid cassette valve chambers and pumpchamber. Valves 120 also control air to seal the cassette for operationand to pressurize a bladder that retracts an occluder that otherwise isclosed to clamp off all fluid lines for safety purposes. Pneumaticreservoirs 140 are shown below schematically in FIGS. 10 to 11.

The integrated pneumatic reservoirs 140 have multiple inlets and outletsin one embodiment, which are bores or holes 128 in plate 104 of manifoldassembly 100 in one embodiment. As seen in FIGS. 6 through 8, the bores128 run directly from one of the integrated reservoirs 140 to a valve120, a pressure sensor, etc. One advantage of the direct connection isthat the pressure sensor reads the actual pressure in the reservoir 140,not the pressure in a line connected to the reservoir, which can differfrom the actual reservoir pressure when air is flowing into or from thereservoir 140.

Another advantage of communicating pneumatic reservoirs 140 of manifoldassembly 100 with valves 120 via individual bores 128 is that if liquidis sucked into the manifold 100, e.g., in a situation in which sheetingon the disposable cassette has a hole located adjacent to one of thecassette's valves, liquid damage is mitigated. With assembly 100, fluidpulled into the assembly flows into one solenoid valve 120 only, afterwhich the fluid discharged directly through a bore 128 associated withthat valve 120 into Neg P Tank reservoir 140 without contaminating othervalves 120 or other components. Thus, only a small portion of thepneumatic system might need replacing.

Gasket 142 seals pneumatic reservoirs 140 to bottom plate 104. Ventfilters 144 minimize the sound produced when air enters (e.g., from POST TANK or NEG P TANK as seen in FIGS. 10 and 11) and/or exits manifoldassembly 100 and prevents particulate matter from entering manifoldassembly 100 along with air.

Manifold assembly 100 includes a pneumatic pump 146 marked as PUMP inFIGS. 10 and 11. Pneumatic pump 146 pressurizes pneumatic reservoirs 140and the sealing bladders shown in FIGS. 10 and 11. The heads 156 of pump146 are attached to bottom plate 104 using longer screws 148 on one endand clamp 150 and screws 112 on the other end. Electrometric seals(o-ring, quad-ring, quad-seal, etc.) 110 seal the pneumatic connectionof the inlets and outlets of pump 146 to bottom plate 104. A thermallyconductive pad 152 (e.g., Bergquist Gap Pad, Bergquist Sil Pad, DowCorning TP 1500 or 2100, Fujipoly Sarcon, Laird T-Pli, T-Flex andT-Putty, or 3M 5507S) thermally links the motor 154 from pump 146 tobottom plate 104, so that bottom plate 104 becomes a heat sink for motor154 and pump 146, absorbing the thermal energy that motor 154 creates.Bottom plate 104 is accordingly made of aluminum or other thermallyconducting material in one embodiment. The thermal connection viathermally conductive pad 152 has been found to lower the operatingtemperature of pump motor 154 from around 100° C. to around 60° C.,which should increase the life expectancy of pump 146.

The mounting and thermal coupling of pump 146 to bottom plate 104 alsoincreases the effective mass of pump 146, so that pump 146 producessound having a lower (and less bothersome) frequency and magnitude.Further, in one embodiment, manifold Assembly 100 is mounted within asealed (potentially air tight), acoustically insulated enclosure,further reducing magnitude of sound emanating from the enclosure. Thelower operating temperature of pump 104 promotes use of the enclosurewithout over heating the manifold assembly.

Referring now to FIGS. 9A to 9D, manifold assembly 180 illustrates onealternative manifold of the present disclosure. Here, pump 146 islocated on the upper surface of the assembly with headers 108 and 116and PCB 118. Mounting pump 146 as shown in FIG. 9A is advantageousbecause the pump is more accessible for servicing and because themanifold assembly is not as tall. Air reservoirs 140 located on theunderside of manifold assembly 180 can be longer and do not need to haveas much depth to achieve the same volume. The pump inlet and outletports of pump 146 can attach directly to the manifold using o-ringconnections. Or, short lengths of flexible tubing can be bent in au-shape and connect barbed ports located on the pump heads 156 of pump146 to barbed fittings located on the underside of the plate upon whichthe pump heads 156 and pump 146 are mounted.

Locating pump 146 on the upper surface of the assembly allows onlyalternative upper plate 202 to be made of metal, e.g., aluminum.Alternative lower plate 204 and intermediate plate 208 can be made ofplastic. Upper plate 202 is threaded to accept screws inserted throughheaders 108 and 116 and plates 204 and 208 to bolt those headers andplates to upper plate 202. Alternative gaskets 206 a and 206 b arelocated between intermediate plate 208 and upper and lower plates 202and 204, respectively, to seal integral flow paths located on theinsides of plates 202 and 204 (like paths 134 and 138 of FIG. 7) andaround valve ports. Middle plate 208 separates gaskets 206 a and 206 band provides a surface against which gaskets 206 a and 206 b cancompress.

FIG. 9B shows pump 146 removed to illustrate that the pump mounts toelastomeric sealing inserts 214 placed in intermediate plate 208. FIGS.9A and 9B illustrate that clamp 150 and conductive pad 152 connect tometallic upper plate 202 in the illustrated embodiment, so that theabove-described heat sinking can occur. Upper plate 202 includes arecessed area 216 with a saddle that is designed for the heat sinkmounting of pump 146 to upper plate 202.

Recessed area 216 forms or includes a saddle that pump motor 154 fitsinto. The saddle conducts the heat from pump motor 154 into upper plate202, which is the only metallic plate as discussed in one embodiment.Top plate 202 includes all of the tapped holes for pump 146 and theother components of system 180. The outlet ports of heads 156 seal tomiddle plate 208, however, there is very little heat conducted from pumpheads 156 to middle plate 208. Instead, air that is being pumped takesheat away from the pump heads 156 and so acts as a coolant.

FIGS. 9C and 9D show different views of lower plate 204, which again isplastic in one embodiment. Lower plate includes molded pressurereservoirs 140 and flow paths 218. Features 222 a and 222 b on theunderside of lower plate 204 accommodate filter 136 and elastomericsealing inserts 214. Reservoirs 140, middle plate 208 and tubing headers108 and 116 can all be molded plastic in one embodiment, reducing weightand cost.

Pneumatic System Configurations

Referring now to FIG. 10, schematic 200 illustrates one pneumaticschematic for manifold assembly 100 shown in FIGS. 4 to 8 and manifoldassembly 180 of FIG. 9. FIG. 10 shows twelve valves on the left bank ofvalves, which correspond to the twelve valves 120 shown mounted on theleft side of PCB 118 in FIGS. 4, 7 and 9. Likewise, the fourteen valvesshown on the right bank of valves of schematic 200 correspond to thefourteen valves 120 shown on the right side of PCB 118 in FIGS. 4, 7 and9. Schematic 200 of FIG. 10 includes a valve labeled B5/NV that is usedto lower the vacuum level in negative pressure tank (NEG P Tank) 140when fluid is to be drained from the patient instead of a supply bag.Previously, the equivalent of air pump 146 of FIG. 10 would be turnedoff and the equivalent of valve D0 (12) of FIG. 10 would be energized,so that air could bleed through air pump 146, lowering the vacuum levelin Neg P Tank 140. The need for the vacuum pump to bleed through thepump severely limited the choice of air pumps that could be used becausethe vast majority of available air pumps do not allow a vacuum to bebled through the pump.

In schematic 200 of FIG. 10, pneumatic pump 146 includes two heads 156(see also FIGS. 5 and 8) having inlets and outlets connected inparallel. Dual heads 156 individually pressurize reservoirs 140simultaneously in the embodiment shown in schematic 210 of FIG. 11. Onehead is dedicated to pressurizing positive pressure reservoir (Pos P (LoPos) tank) 140. Positive pressure reservoir 140 in one embodiment iscontrolled at about 1.5 psig when pumping to the patient or at about 5.0psig when pumping to a solution bag or drain line. The other head 156 isdedicated to evacuating negative pressure reservoir (Neg P tank) 140.Negative pressure reservoir 140 in one embodiment is controlled at about−1.5 psig when pumping from the patient or at about −5.0 psig whenpumping from a solution bag. Because pump 146 does not have to switchback and forth between reservoirs 140, the reservoirs 140 are filled ona more constant and smooth basis, reducing noise and reducing the energyrequired to operate pump 146. Halving the flow to dual pump heads 156reduces the pressure losses due to flow restrictions to nearlyone-quarter of their original value. Running each reservoir at half flowrate reduces noise because the inrush of air to positive reservoir 140or from negative reservoir 140 is less severe.

Both schematics 200 and 210 further include an inline filter 136 thatprevents particulate generated at air pump 146 from entering manifoldassembly 100 or 180. Schematics 200 and 210 also include a manuallyoperated selector valve 130 (see FIGS. 4 and 6) for diverting a pathwayin the manifold to an outside calibration port.

Pneumatic schematic 210 of FIG. 11 shows an alternative pneumaticconfiguration for manifold assemblies 100 and 180 of the presentdisclosure. Schematic 210 of FIG. 11 differs from schematic 200 of FIG.10 in one respect because schematic 210 includes a three-way valve A6that replaces a two-way Hi-Lo valve A6 of FIG. 11. Three-way valve A6 ofsystem 10 allows air pump 146 to maintain the pressure in the Pos P (LoPos) tank 140 directly, while isolating an occluder tank 56 and Pos T(High Pos) tank (bladder 54 of FIG. 1).

The occluder tank 56 and Pos T tank 54 are in one embodiment bladdersthat can expand and contract with pressure changes. Bladder as usedherein includes, without limitation, balloon type bladders and bellowstype bladders. The force created by the Pos T bladder 54 seals adisposable cassette against a cassette holder 22 on machine 10 thatoperates one or more pump chamber and valve chamber located within thecassette. In one embodiment, pump 146 pressurizes both bladders 54 or 56to about 7.1 psig. Previously, the bladder pressures have fluctuatedbetween about 5 psig and 7.1 psig. The bladder pressures for schematic210 of the present disclosure however have been narrowed to fluctuatebetween about 6.8 psig and about 7.1 psig. For schematic 200, thecassette sealing bladder pressure would normally fluctuate between 6.8psig and 7.1 psig but can fall as low as five psig if the occluder isclosed and re-opened. The system of schematic 210 eliminates thepossibility of falling to five psig.

The force created by the occluder bladder 56 retracts an occluder bar bycompressing plural coil springs, allowing fluid to flow to and from thecassette during normal operation. If occluder bladder 56 is notretracted, the occluder will extend, pinching the tubing lines that leadfrom the cassette to the patient, heater bag, supply bags and drain lineso that fluid movement is prevented. Three-way valve A6 closes offcassette bladder 54 and occluder bladder 56 whenever the air pump has topressurize Pos P Tank 140, so that no air is stolen from the bladder.For example, in one implementation, when machine 10 is pumping fluid tothe patient, the Pos P (Low Pos) tank 140 pressure is maintained at 1.5psig.

A replenishment of a heater bag (stored on tray 16 shown in FIG. 1)follows each patient fill, which requires five psig. To change pressurein Pos P tank 140 from 1.5 to five psig, PCB 118 energizes three-wayvalve A6, closing off the cassette sealing bladder and occluder bladder56 supply lines so that the pressure in the bladders cannot fall. Thepressure in the Pos T bladder 54 and occluder bladder 56 can momentarilyfall to as low as about five psig at this time, which is close to thepressure needed to retract the occluder, i.e., the occluder couldactuate inadvertently generating a creaking noise if the two-way valveof schematic 200 is used instead of the three-way isolating valve ofschematic 210. In schematic 210, the pressure in the Pos T bladder 54and occluder bladder 56 will not change upon a replenishment of theheater bag because pneumatic system 210 uses three-way valve A6.

In another example, if the pressure in Pos T bladder 54 falls to as lowas about five psig, the seal between the disposable cassette and machineinterface can be broken momentarily. It is possible that the seal willnot be recreated when the pressure in Pos T bladder 54 is increased toits normal operating pressure of about 7.1 psi. Machine 10 withoutthree-way valve A6 (e.g., schematic 200 of FIG. 10) can be configured todetect this leak by performing a pressure decay test on Pos T bladder 54and post an alarm when such leak is detected. The alarm is cleared bycycling the power off and back on. If the pressure is below about 4.5psig when the power comes back on, the therapy is terminated because thecassette seal is determined to have been broken. The machine operatingaccording to schematic 210 however avoids this alarm by isolating Pos Tbladder 54 from the pneumatic lines filling the occluder bladder 56and/or the Pos P Tank 140, ensuring that Pos T bladder 54 is at thehigher pressure.

Schematic 210 allows pump 146 to maintain the pressure in Pos Preservoir 140 directly, so that pump 146 only has to pump against either1.5 or 5 psig. In schematic 200, Pos P reservoir 140 is maintainedindirectly through Pos T bladder 54, which requires pump 146 to pumpagainst 7.1 psig of Pos T bladder 54. Pump 146 generates less noise andless heat when it pumps against the lower pressure. Also, when the 7.1psig Pos T bladder 54 and the occluder bladder 56 are connected to Pos Preservoir 140 by valve A6 in system 200, the 7.1 psig source produces arush of air to the 1.5 psig destination. This rush of air generates anoticeable audible noise.

In another example, if the pressure of occluder bladder 56 falls toabout 5 psig from 7.1 psig, the load on the compression springsdecreases allowing the springs to extend the occluder partway but notenough to completely pinch-off the flow of fluid through the tubingleading to or from the cassette. The partial movement of the occluderresults in an audible creaking noise that can wake up a sleepingpatient. The isolation of three-way valve A6 prevents such partialocclusion from occurring.

Schematic 210 of FIG. 11 also arranges the dual heads 156 of pneumaticpump 146 so that one head is dedicated to positive pressure generation,while the other head is dedicated to negative pressure generation. Theresult is a lower rate of air flow through the system when the Pos Tbladder 54, Pos P reservoir 140, Neg P reservoir 140 or occluder bladder56 are being maintained, which generates less noise.

As seen additionally in FIG. 12, whenever the positive pressure ofpositive pump head 156 or the negative pressure of pump head 156 is notbeing used, the resulting air flows are diverted through a circuit 220containing free-flow orifices 158, 160 and 162, operate as shown below.Free-flow orifices 160 and 162 create a resistance to airflow thatmaintains the sound produced by the air flow at a pitch that is veryclose to the sound that the pump produces when it is pressurizing thecomponents of schematic 210. Although the “free flow” orifices 160 and162 do not reduce the air flow or the sound, the orifices make the soundless offensive to the patient because the sound is maintained at the lowpump frequency.

FIGS. 12 and 13 show noise reduction circuit 220 in two valve states.FIG. 12 is the de-energized, recirculation, noise reducing state. FIG.13 is the energized, pressure-applying state. In FIG. 12, valves C5 andD0 (also seen in FIG. 11) are in the de-energized state. Each pump head156 pumps in a recirculation loop with the outlet flow being directedback to the pump head inlet. Positive pressure orifice 162 and negativepressure orifice 160 maintain a partial load on positive pump head 156and negative pump head 156, respectively.

When valves C5 and D0 switch state as shown in FIG. 13, the change inthe load on the pump heads 156 is small, so that the pitch and amplitudedifference between when pump 146 is running in (i) free flow (FIG. 12)and (ii) both pressure and vacuum (FIG. 13) is minimized. Further, thechange in the load on the negative pump head 156 is small, so that thepitch and amplitude difference between when pump 146 is running in (i)free flow (FIG. 12) and (iii) vacuum only (not shown but valve D0 is asin FIG. 13, while valve C5 is as in FIG. 12) is minimized. Stillfurther, the change in the load on the negative pump head 156 is small,so that the pitch and amplitude difference between when pump 146 isrunning in (i) free flow (FIG. 12) and (iv) pressure only (not shown butvalve D0 is as in FIG. 12, while valve C5 is as in FIG. 13) isminimized. It should also be appreciated that pitch and amplitudedifference is minimized when switching from: state (ii) to state (i),(iii) or (iv); state (iii) to state (i), (ii) or (iv); and state (iv) tostate (i), (ii) or (iii).

Schematic 210 of FIG. 11 also includes plural filters 144 (FIG. 8)integrated into manifold assembly 100 in places that an inrush of flowcan occur that could generate noise of a higher frequency and magnitudethan a baseline noise. For example, one of the filters 144 reduces themagnitude of the noise that Pos P tank 54 generates when pressure ischanged from 1.5 psig to 5 psig. Another filter 144 reduces themagnitude of the noise that is generated when the occluder bladder ispressurized. Still another pair of filters 144 reduces the magnitude ofthe noise that the connection of the pumping chambers 140 to thevolumetric reference chambers located at cassette interface 26 (FIG. 3)creates during the fluid measurement process. Multi-layered manifoldassembly 100 accommodates placement of the above filter elements 144economically wherever they are needed.

Schematic 210 of FIG. 11 shows yet another improvement for integratedmanifold assembly 100 or 180. A one-way flow check valve 212 is includedin the conduit supplying pressure to the valve, which supplies PosTbladder 54, which in turn maintains the pressure that seals the cassetteand its fluid pathways. Cassette-sealing bladder 54 with check valve 212cannot lose pressure when or after occluder bladder 56 is pressurized.Check valve 212 thus prevents a loss of the seal between the cassetteand gasket located in the cassette interface 26 due to a momentary lossof pressure of occluder bladder 56. A solenoid valve can be used insteadof the one-way check valve.

It should be understood that various changes and modifications to thepresently preferred embodiments described herein will be apparent tothose skilled in the art. Such changes and modifications can be madewithout departing from the spirit and scope of the present subjectmatter and without diminishing its intended advantages. It is thereforeintended that such changes and modifications be covered by the appendedclaims.

The invention is claimed as follows:
 1. A pneumatic system for a medicalfluid machine operating a medical fluid cassette, the pneumatic systemcomprising: an interface for supplying positive pneumatic pressure andnegative pneumatic pressure to the medical fluid cassette; a source ofpositive pneumatic pressure; a source of negative pneumatic pressure;and a pneumatic pump including a first head and a second head, whereinthe first head is dedicated to supplying positive pneumatic pressure tothe positive pneumatic pressure source and the second head is dedicatedto supplying negative pneumatic pressure to the negative pneumaticpressure source.
 2. The pneumatic system of claim 1, which is configuredto supply positive pneumatic pressure from the first head to thepositive pneumatic pressure source and negative pressure from the secondhead to the negative pneumatic pressure source simultaneously.
 3. Thepneumatic system of claim 1, which includes a valve manifold assemblycommunicating pneumatically between the sources of positive and negativepneumatic pressure and the medical fluid cassette interface.
 4. Thepneumatic system of claim 3, wherein at least one of the positivepneumatic pressure source, the negative pneumatic pressure source, orthe pneumatic pump is mounted to the valve manifold assembly.
 5. Thepneumatic system of claim 1, wherein the interface includes a machineinterface against which the medical fluid cassette is pressed.
 6. Thepneumatic system of claim 1, which is configured to pneumaticallyisolate the positive pneumatic pressure source from the negativepneumatic pressure source.
 7. The pneumatic system of claim 6, which isconfigured to pneumatically isolate at least one bladder from at leastone of the positive pneumatic pressure source or the negative pneumaticpressure source.
 8. A pneumatic system for a medical fluid machineoperating a medical fluid cassette, the pneumatic system comprising: aninterface for supplying positive pneumatic pressure and negativepneumatic pressure to the medical fluid cassette; a source of positivepneumatic pressure; a source of negative pneumatic pressure; and apneumatic pump configured to simultaneously supply (i) positivepneumatic pressure to the positive pneumatic pressure source and (ii)negative pneumatic pressure to the negative pneumatic pressure source.9. The pneumatic system of claim 8, wherein the pneumatic pump includesa first head dedicated to supplying positive pneumatic pressure and asecond head dedicated to supplying negative pneumatic pressure.
 10. Thepneumatic system of claim 9, wherein each of the first and second pumpheads is configured to be mounted to a valve manifold assembly.
 11. Thepneumatic system of claim 8, wherein the positive pneumatic pressuresource is a first positive pneumatic pressure, and which includes asecond positive pneumatic pressure source, wherein one of the first andsecond positive pneumatic pressure sources is a high positive pressuresource and the other of the first and second positive pressure sourcesis a low positive pressure source.
 12. The pneumatic system of claim 11,which is configured to place (i) the high positive pneumatic pressuresource in pneumatic communication with at least one bladder and (ii) thelow pneumatic pressure source in operable communication with at leastone pump chamber of the medical fluid cassette.
 13. The pneumatic systemof claim 8, wherein the interface includes a machine interface againstwhich the medical fluid cassette is pressed.
 14. The pneumatic system ofclaim 8, wherein the interface includes at least one pneumatic tubingconnection for receiving at least one of positive or negative pneumaticpressure.
 15. A method for pneumatically operating a medical fluidmachine in operable communication with a medical fluid cassette, themethod comprising: simultaneously supplying (i) positive pneumaticpressure to a positive pneumatic pressure source and (ii) negativepneumatic pressure to a negative pneumatic pressure source; allowing themedical fluid cassette to receive positive pneumatic pressure from thepositive pneumatic pressure source; and allowing the medical fluidcassette to receive negative pneumatic pressure from the negativepneumatic pressure source.
 16. The method of claim 15, wheresimultaneously supplying (i) and (ii) includes simultaneously supplying(i) and (ii) from a same pneumatic pump.
 17. The method of claim 16,which includes reducing energy required to operate the pneumatic pump bysimultaneously supplying (i) and (ii).
 18. The method of claim 15, whichincludes reducing noise by simultaneously supplying (i) and (ii). 19.The method of claim 15, which includes supplying positive pneumaticpressure to a plurality of positive pneumatic pressure sources.
 20. Themethod of claim 15, which includes lessening a severity of an inrush ofair to positive pneumatic pressure source or from negative pneumaticpressure source by simultaneously supplying (i) and (ii).